CAs are involved in a variety of biological processes, including respiration, calcification,acid-base balance, bone resorption and the formation of aqueous humor,cerebrospinal fluid, saliva and gastric juice. They show extensive diversity in distribution and in their subcellular localization. The human CA9,CA12 and CA14 genes, which map to chromosomes 9p13.3, 15q22 and 1q21, respectively, encode transmembrane proteins that have unique patterns of tissue-specific expression. CA IX is specifically expressed in clear-cell renal carcinomas, whereas CA XII is highly expressed in normal tissues, such as kidney, colon and pancreas.